Direct-drive wind turbine machine-side direct current impedance and admittance modeling method, medium and system

Abstract

The application discloses a direct-drive wind turbine generator set machine-side DC impedance and admittance modeling method, medium and system, comprising: establishing a small signal model of a converter control link, a small signal model of a PWM link, a small signal model of machine-side converter power conservation, and a small signal model of machine-side PMSG circuit relationship; collecting converter parameters; through simultaneous transformation of the small signal model of the converter control link, the small signal model of the PWM link, the small signal model of the machine-side converter power conservation and the small signal model of the machine-side PMSG circuit relationship, a direct-drive wind turbine generator set machine-side DC impedance and admittance model is established, and the direct-drive wind turbine generator set machine-side DC impedance and admittance is calculated by using the converter parameters. The embodiment of the application considers PMSG circuit equations, control characteristics of a machine-side converter and PWM modulation characteristics, and can accurately represent dynamic characteristics of a machine-side system.

Description

Technical Field

[0001] This invention relates to the field of power system stability analysis and control technology, and in particular to a method, medium and system for modeling the DC impedance and admittance of a direct-drive wind turbine generator. Background Technology

[0002] In recent years, wind power generation has developed rapidly and gradually occupied a dominant position in the power system. However, the interaction between direct-drive wind turbines and the power grid can easily cause broadband oscillations, seriously threatening the safe operation of the power system. Impedance and admittance-based analysis methods have become the mainstream method for analyzing the oscillation stability of wind power grid-connected systems. To ensure the accuracy of stability assessment, it is necessary to establish accurate impedance and admittance models for direct-drive wind turbines. However, most existing studies neglect the machine-side system (i.e., the permanent magnet synchronous generator (PMSG) and the machine-side converter), using only the grid-side converter to characterize the overall dynamic characteristics. When the machine-side converter adopts constant torque and speed control, the machine-side system is simply equivalent to a constant power source; when the machine-side converter adopts constant DC voltage control, the machine-side system is simply equivalent to a constant voltage source. However, research has found that the impedance and admittance models obtained by neglecting the machine-side system are difficult to accurately characterize the dynamic characteristics of direct-drive wind turbines, and the stability analysis results contain errors. Therefore, it is necessary to establish a machine-side DC impedance and admittance model for direct-drive wind turbines.

[0003] Existing technologies neglect the characteristics of the PMSG circuit, the control loop of the machine-side converter, and the pulse width modulation (PWM) modulation characteristics, simply equating the machine-side system to a constant power source or constant voltage source. However, this equivalence cannot fully simulate the dynamic characteristics of the machine-side system, leading to errors in the oscillation stability analysis results of direct-drive wind farms. Therefore, it is necessary to propose a modeling method for the DC impedance and admittance of direct-drive wind turbines that considers the characteristics of the PMSG circuit, the control characteristics of the machine-side converter, and the PWM modulation characteristics. Summary of the Invention

[0004] This invention provides a method, medium, and system for modeling the DC impedance and admittance of a direct-drive wind turbine generator, which solves the problem that existing technologies simply equate the generator-side system to a constant power source or constant voltage source, which cannot fully simulate the dynamic characteristics of the generator-side system and leads to errors in the oscillation stability analysis results of direct-drive wind farms.

[0005] Firstly, a method for modeling the DC impedance and admittance of a direct-drive wind turbine generator side is provided, including: Establish small-signal models for the converter control loop, PWM loop, generator-side converter power conservation, and generator-side PMSG circuit relationship. The converter parameters are collected, including: the steady-state quantity of the converter DC side current, the steady-state quantity of the converter DC voltage, the steady-state quantity of the d-axis measurement value and the steady-state quantity of the q-axis measurement value of the converter AC side current, the steady-state quantity of the d-axis reference value and the steady-state quantity of the q-axis reference value of the converter AC side voltage, and the steady-state quantity of the d-axis measurement value and the steady-state quantity of the q-axis measurement value of the converter AC side voltage. By combining and transforming the small-signal models of the converter control loop, the PWM loop, the generator-side converter power conservation, and the generator-side PMSG circuit relationship, a generator-side DC impedance and admittance model for the direct-drive wind turbine is established. The generator-side DC impedance and admittance of the direct-drive wind turbine are then calculated using the converter parameters.

[0006] In a second aspect, a computer-readable storage medium is provided, wherein computer program instructions are stored on the computer-readable storage medium; when the computer program instructions are executed by a processor, they implement the direct-drive wind turbine generator side DC impedance and admittance modeling method as described in the first aspect embodiment.

[0007] Thirdly, a system for modeling the DC impedance and admittance of a direct-drive wind turbine generator is provided, comprising: a computer-readable storage medium as described in the embodiments of the second aspect.

[0008] Thus, the embodiments of the present invention take into account the PMSG circuit equations, the control characteristics of the machine-side converter, and the PWM modulation characteristics, and can accurately characterize the dynamic characteristics of the machine-side system. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a flowchart of the direct-drive wind turbine generator side DC impedance and admittance modeling method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the circuit topology and control strategy of the direct-drive wind turbine generator set according to an embodiment of the present invention. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] like Figure 2 As shown, the PMSG is directly connected to the machine-side converter, and the control loop of the machine-side converter is inside the dashed box in the figure. Based on this structure, this embodiment of the invention discloses a method for modeling the machine-side DC impedance and admittance of a direct-drive wind turbine. Figure 1 As shown, the method of this embodiment of the invention includes the following steps: Step S101: Establish the small-signal model of the converter control loop, the small-signal model of the PWM loop, the small-signal model of the power conservation of the machine-side converter, and the small-signal model of the relationship between the machine-side PMSG circuit.

[0013] 1. Small-signal model of converter control loop Specifically, the small-signal model of the converter control loop includes: the small-signal model of the converter outer loop and the small-signal control model of the converter inner loop.

[0014] (1) Small-signal model of converter outer loop The small-signal model of the converter's outer loop is obtained by harmonic linearization of the transfer function of the outer loop control element. Harmonic linearization is a conventional method and will not be elaborated upon here.

[0015] The outer loop of the generator-side converter utilizes a PI control loop only for the q-axis to achieve constant DC voltage control, while the d-axis directly provides the AC side voltage of the converter with a reference value of zero. Therefore, the transfer function of the outer loop control loop includes: .

[0016] in, This is the d-axis reference value for the AC side voltage of the converter. This is the q-axis reference value for the AC side voltage of the converter. This is the reference value for the DC voltage of the converter. This is the measured value of the DC voltage of the converter. This is the transfer function for DC voltage control. , This is the proportional gain of the DC voltage control circuit. This is the integral gain of the DC voltage control circuit. s It is a differential operator.

[0017] Specifically, the small-signal model of the converter outer loop includes: .

[0018] in, This represents the disturbance to the d-axis reference value of the AC side current of the converter. This represents the disturbance to the q-axis reference value of the AC side current of the converter. This represents the disturbance in the measured DC voltage value of the machine-side converter.

[0019] (2) Small-signal control model of converter inner loop Specifically, the converter inner-loop small-signal control model includes: .

[0020] in, This represents the disturbance to the d-axis reference value of the AC side voltage of the converter. This represents the disturbance to the q-axis reference value of the AC side voltage of the converter. This represents the disturbance in the d-axis measurement of the AC side current of the converter. This represents the disturbance in the q-axis measurement of the AC side current of the converter. Let be the transfer function for the inner current loop control. , is the proportional gain of the current inner loop control element, and is the integral gain of the current inner loop control element. The other symbols have the same physical meaning as the previously mentioned symbols and will not be repeated here.

[0021] 2. Small-signal model of PWM stage The small-signal model of the PWM circuit is obtained by harmonic linearization of the calculation equations for the d-axis and q-axis measurements of the AC side voltage of the converter.

[0022] The reference voltage is used to generate switching pulse signals through a PWM circuit. Therefore, the equations for calculating the d-axis and q-axis measurements of the AC side voltage of the converter can be expressed as follows: .

[0023] in, This represents the d-axis measurement value of the AC side voltage of the converter. This is the q-axis measurement value of the AC side voltage of the converter. This is the d-axis reference value for the AC side voltage of the converter. This is the q-axis reference value for the AC side voltage of the converter. For modulation coefficients, generally... =2 / The other symbols have the same physical meaning as the aforementioned symbols, and will not be repeated here.

[0024] Specifically, the small-signal model of the PWM stage includes: .

[0025] in, This represents the disturbance in the d-axis measurement of the AC side voltage of the converter. This represents the disturbance in the q-axis measurement of the AC side voltage of the converter. This is a steady-state quantity representing the d-axis reference value of the AC side voltage of the converter. This is a steady-state quantity representing the q-axis reference value of the AC side voltage of the converter. The steady-state quantity of the DC voltage of the converter. Other symbols have the same physical meaning as the symbols mentioned above, and will not be repeated here.

[0026] 3. Small-signal model of power conservation in machine-side converter The small-signal model for power conservation in the machine-side converter is obtained by harmonic linearization of the power conservation equation of the machine-side converter under the conditions of neglecting the losses of power electronic switching devices and assuming that the power of the DC port and AC port of the machine-side converter are equal.

[0027] Specifically, the power conservation equations for the machine-side converter include: .

[0028] in, This is the DC side current of the converter, with the direction of flow into the converter being positive. , , This is the steady-state quantity of the AC side current measured on the d-axis of the converter. This is the steady-state quantity of the q-axis measurement of the AC side current of the converter. Other symbols have the same physical meaning as those previously mentioned and will not be repeated here.

[0029] Specifically, the small-signal power conservation model for the generator-side converter includes: .

[0030] in, This represents the disturbance to the DC-side current of the converter. The steady-state quantity of the DC-side current of the converter. This is the steady-state quantity of the d-axis measurement of the AC side voltage of the converter. This represents the steady-state quantity of the q-axis measurement of the AC side voltage of the converter. Other symbols have the same physical meaning as those previously mentioned and will not be repeated here.

[0031] 4. Small-signal model of PMSG circuit relationship on the machine side Specifically, the small-signal model of the PMSG circuit relationship on the machine side includes: .

[0032] in, For PMSG stator resistors, For PMSG stator inductors, This represents the PMSG electromagnetic angular frequency. Other symbols have the same physical meaning as those previously mentioned and will not be repeated here.

[0033] Step S102: Collect converter parameters.

[0034] Specifically, the converter parameters include: the steady-state quantity of the converter DC side current, the steady-state quantity of the converter DC voltage, the steady-state quantity of the converter AC side current d-axis measurement value and q-axis measurement value, the steady-state quantity of the converter AC side voltage d-axis reference value and q-axis reference value, and the steady-state quantity of the converter AC side voltage d-axis measurement value and q-axis measurement value.

[0035] Step S103: By combining and transforming the small-signal models of the converter control loop, the PWM loop, the power conservation small-signal model of the generator-side converter, and the small-signal model of the generator-side PMSG circuit relationship, a model of the generator-side DC impedance and admittance of the direct-drive wind turbine is established, and the generator-side DC impedance and admittance of the direct-drive wind turbine are calculated using converter parameters.

[0036] The equivalent impedance and admittance models of the direct-drive wind turbine generator side system obtained by combining the following are: .

[0037] in, The DC equivalent impedance of the direct-drive wind turbine generator (i.e., PMSG + generator-side converter) is... This represents the DC equivalent admittance of the direct-drive wind turbine generator (i.e., PMSG + generator-side converter). Other symbols have the same physical meaning as those previously mentioned and will not be repeated here.

[0038] Among them, the solution used , , , , It can be given in advance based on experience. , This is determined by the properties of the PMSG stator itself. These are the rated parameters for PMSG. , This is the result of actual measurement in step S102.

[0039] By substituting the collected converter parameters, the DC impedance and admittance of the direct-drive wind turbine can be calculated.

[0040] The DC impedance and admittance of a direct-drive wind turbine can accurately characterize the PMSG circuit, the control characteristics of the turbine-side converter, and the PWM modulation characteristics; it can also be used to analyze the broadband oscillation stability of a direct-drive wind turbine. If the turbine has a risk of broadband oscillation instability, the control parameters of the outer loop control and inner loop control can be adjusted appropriately until the turbine is free from instability risk. Therefore, the equivalent impedance and admittance model of the turbine-side system of the direct-drive wind turbine in this embodiment of the invention can be used for broadband oscillation stability analysis of direct-drive wind turbines and for control parameter tuning.

[0041] Furthermore, embodiments of the present invention also provide a computer-readable storage medium storing computer program instructions; when the computer program instructions are executed by a processor, they implement the direct-drive wind turbine generator-side DC impedance and admittance modeling method as described in the above embodiments.

[0042] Furthermore, embodiments of the present invention also provide a modeling system for the DC impedance and admittance of a direct-drive wind turbine generator, comprising: a computer-readable storage medium as described in the above embodiments.

[0043] In summary, the embodiments of the present invention take into account the PMSG circuit equations, the control characteristics of the machine-side converter, and the PWM modulation characteristics, and can accurately characterize the dynamic characteristics of the machine-side system.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for modeling the DC impedance and admittance of a direct-drive wind turbine generator, characterized in that, include: Establish small-signal models for the converter control loop, PWM loop, generator-side converter power conservation, and generator-side PMSG circuit relationship. The converter parameters are collected, including: the steady-state quantity of the converter DC side current, the steady-state quantity of the converter DC voltage, the steady-state quantity of the d-axis measurement value and the steady-state quantity of the q-axis measurement value of the converter AC side current, the steady-state quantity of the d-axis reference value and the steady-state quantity of the q-axis reference value of the converter AC side voltage, and the steady-state quantity of the d-axis measurement value and the steady-state quantity of the q-axis measurement value of the converter AC side voltage. By combining and transforming the small-signal model of the converter control loop, the small-signal model of the PWM loop, the small-signal model of the power conservation of the machine-side converter, and the small-signal model of the relationship of the machine-side PMSG circuit, a model of the machine-side DC impedance and admittance of the direct-drive wind turbine is established, and the machine-side DC impedance and admittance of the direct-drive wind turbine are calculated using the converter parameters. The small-signal model of the converter control loop includes: the small-signal model of the converter outer loop; the small-signal model of the converter outer loop is obtained by harmonic linearization of the transfer function of the outer loop control loop. The transfer function of the outer loop control element includes: ； The small-signal model of the converter outer loop includes: ； in, This is the d-axis reference value for the AC side voltage of the converter. This is the q-axis reference value for the AC side voltage of the converter. This is the reference value for the DC voltage of the converter. This is the measured value of the DC voltage of the converter. This represents the disturbance to the d-axis reference value of the AC side current of the converter. This represents the disturbance to the q-axis reference value of the AC side current of the converter. This represents the disturbance to the measured DC voltage value of the generator-side converter. This is the transfer function for DC voltage control. , This is the proportional gain of the DC voltage control circuit. This is the integral gain of the DC voltage control circuit. s It is a differential operator; The small-signal model of the converter control loop also includes: the small-signal control model of the converter inner loop; The converter inner loop small-signal control model includes: ； in, This represents the disturbance to the d-axis reference value of the AC side voltage of the converter. This represents the disturbance to the q-axis reference value of the AC side voltage of the converter. This represents the disturbance in the d-axis measurement of the AC side current of the converter. This represents the disturbance in the q-axis measurement of the AC side current of the converter. Let be the transfer function for the inner current loop control. , This is the proportional gain of the inner current control loop. The integral gain of the inner current loop control loop; The small-signal model of the PWM link is obtained by harmonic linearization of the calculation equations for the d-axis and q-axis measurements of the AC side voltage of the converter. The calculation equations for the d-axis and q-axis measurements of the AC side voltage of the converter include: ； The small-signal model of the PWM stage includes: ； in, This represents the d-axis measurement value of the AC side voltage of the converter. This is the q-axis measurement value of the AC side voltage of the converter. This is the d-axis reference value for the AC side voltage of the converter. This is the q-axis reference value for the AC side voltage of the converter. This represents the disturbance in the d-axis measurement of the AC side voltage of the converter. This represents the disturbance in the q-axis measurement of the AC side voltage of the converter. This is a steady-state quantity representing the d-axis reference value of the AC side voltage of the converter. This is a steady-state quantity representing the q-axis reference value of the AC side voltage of the converter. This represents the steady-state quantity of the DC voltage of the converter. The modulation coefficient, =2 / ; The small-signal model of the machine-side PMSG circuit relationship includes: ； in, For PMSG stator resistors, For PMSG stator inductors, It represents the electromagnetic angular frequency of PMSG.

2. The method for modeling the DC impedance and admittance of a direct-drive wind turbine generator according to claim 1, characterized in that, The small-signal model for power conservation in the machine-side converter is obtained by harmonic linearization of the power conservation equation of the machine-side converter under the conditions of neglecting the losses of power electronic switching devices and assuming that the power of the DC port and AC port of the machine-side converter are equal. The power conservation equation for the machine-side converter includes: ； The power conservation small-signal model of the machine-side converter includes: ； in, This refers to the DC-side current of the converter. This represents the disturbance to the DC-side current of the converter. The steady-state quantity of the DC-side current of the converter. This is the steady-state quantity of the d-axis measurement of the AC side voltage of the converter. This is the steady-state quantity of the q-axis measurement of the AC side voltage of the converter. This is the steady-state quantity of the AC side current measured along the d-axis of the converter. This is the steady-state quantity of the q-axis measurement of the AC side current of the converter. = + , = + .

3. The method for modeling the DC impedance and admittance of a direct-drive wind turbine generator according to claim 1, characterized in that, The equivalent impedance and admittance model of the direct-drive wind turbine generator side system includes: ； in, The DC equivalent impedance of the direct-drive wind turbine generator. This refers to the DC equivalent admittance of the direct-drive wind turbine generator.

4. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions; when the computer program instructions are executed by a processor, they implement the direct-drive wind turbine generator side DC impedance and admittance modeling method as described in any one of claims 1 to 3.

5. A modeling system for the DC impedance and admittance of a direct-drive wind turbine generator, characterized in that, include: The computer-readable storage medium as described in claim 4.

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